A hybrid vehicle may be equipped with an engine auto-stop system. An engine auto-stop system shuts down the engine during certain periods of vehicle operation to conserve fuel. For example, engine auto-stop may be engaged when the vehicle is stopped at a traffic light or in a traffic jam rather than permitting the engine to idle. The engine may be restarted when the driver releases the brake or actuates the accelerator pedal. The engine may also be started, for example, due to loads on the electrical system. Stopping the engine when it is not needed improves fuel economy and reduces emissions.
Engine auto-stop systems may also pose various challenges. For example, frequent engine stop/start events can cause driver discomfort and starter motor overheating. To prevent excessive engine stop and starter motor overheating, the total number of stop/start events occurring within a time window, along with the starter motor heat accumulated from restarting the engine during the stop/start events, is monitored. Engine stop may be inhibited once an engine stop and/or starter motor heat threshold is reached. In the existing design of engine stop scheduling, the engine stop is inhibited once a limit associated with the number of engine stops permitted within a specified time window is reached and/or a heat threshold is reached.